1. Field of the Invention
The present invention relates to information processing using received signals in a wireless signal receiver, which receives signals transmitted from tags (particularly, RFID tags) and an information providing technology at least using received signals or a distance measurement (estimation) technology using received signals, and more particularly to an information providing system and method that provides suitable information according to the position of a person who is located in an arbitrary place such as a station premise, a street or shopping center, a department store, an art museum, or a theme park.
2. Description of the Related Art
Recently, ubiquitous network environments in which it is possible to access a network anywhere at any time have been developed to realize ubiquitous information society. Especially, the spread of portable information devices using a short-distance wireless technology or a mobile communication network for moving bodies is remarkable. One example of a conventional technology for such a portable information device providing information suitable for a place, where a person who holds the portable information device is located, to the person is described in Japanese Published Unexamined Patent Application No. 2004-112482 (Reference 1). In this technology, a place where a person who holds a wireless LAN terminal such as a PC or PDA is located is specified from the intensity of wireless LAN signals propagated between the wireless LAN terminal and a plurality of base stations such as wireless LAN access points and information optimal for the specified place is provided to the person through the terminal. Another example of this technology is a system which measures the distance between a terminal and base stations based on the length of propagation time of a laser pulse from each base station, specifies a place where a person who holds the terminal is located, and provides information optimal for the place to the user through the terminal.
Another technology is described, for example, in Japanese Published Unexamined Patent Application No. 2002-205888 (Reference 2). In this technology, an inexpensive Radio Frequency Identification (RFID) tag is installed at every position. An ID can be assigned to each RFID tag to uniquely identify each position (or place). Using a passive RFID tag, which requires no power, is cost-efficient. An RFID reader in a system using this technology reads an ID of an RFID tag when a person who holds the reader is near a specific place and specifies the place from the read ID.